A series of experiments is proposed to characterize the lateral hypothalamic (LH) lesion induced reduction in the body protein and lipid tissue masses. The specific tissues sacrificed in reducing body protein, and the role growth hormone may play in these changes will be assessed. The possibility that altered capacities for fat oxidation contribute to lesion-induced body lipid changes will also be examined. In a final series of experiments, the activity of brown adipose tissue and the norepinephrine turnover rate in visceral tissues will be used to assess lesion-induced changes in sympathetic nervous system activity during the acute hypermetabolic phase and during the chronic stage of stable, but reduced, body mass.